The more excess weight a person carries, the greater their risk of certain types of cancer, researchers have found.

The finding comes as obesity rates across the world are increasing sharply due to poor diet and a sedentary lifestyle.

The researchers, from International Agency for Research on Cancer (IARC), found that obesity increased the risk of breast, colon, kidney and oesophageal cancer and cancer of the womb lining.

Governments are still ignoring issues that would make a real difference

Lancet Oncology

They are calling for a concerted effort to tackle obesity by governments, the media, schools and employers.

Writing in the journal Lancet Oncology, they say: "Avoidance of weight gain should become one of the mainstays of chronic disease prevention in modern societies."

They say a large number of new cancers could be avoided if people managed their weight more effectively through diet and exercise.

They estimate that 40% of womb lining cancers, up to 25% of kidney cancers and about 10% of breast and colon cancers would not develop if people avoided putting on excess weight.

And they have calculated that obesity is responsible for 35,000 new cancers each year in the EU.

The researchers say that obesity increases the risk of breast cancer in postmenopausal women by as much as 40%.

Widespread problem

About half of all men and 35% of women in Europe are considered to be overweight.

Obesity in the UK increased by 10% in the decade to 1997.

The researchers say: "About half of the adult population of industrialised countries are insufficiently active in their leisure time and one quarter to one third can be classified as totally inactive."

An editorial in the same journal accuses governments of failing to tackle the problem with sufficient focus.

"Governments are still ignoring issues that would make a real difference," the editorial says.

"Long working hours and high-pressure environments contribute to the general decrease in leisure time and prohibit regular exercise or healthy cooking."